sched: Implement demand based update_cfs_load()

When the system is busy, dilation of rq->next_balance makes lb->update_shares()
insufficiently frequent for threads which don't sleep (no dequeue/enqueue
updates).  Adjust for this by making demand based updates based on the
accumulation of execution time sufficient to wrap our averaging window.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234938.291159744@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 20 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index dadab4d13875..e914a716e1d4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -353,9 +353,16 @@ struct cfs_rq {
          */
         unsigned long h_load;
 
+        /*
+         * Maintaining per-cpu shares distribution for group scheduling
+         *
+         * load_stamp is the last time we updated the load average
+         * load_last is the last time we updated the load average and saw load
+         * load_unacc_exec_time is currently unaccounted execution time
+         */
         u64 load_avg;
         u64 load_period;
-        u64 load_stamp, load_last;
+        u64 load_stamp, load_last, load_unacc_exec_time;
 
         unsigned long load_contribution;
 #endif
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 33f941dcf88c..e7e2f08e6d01 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -539,6 +539,9 @@ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
         return calc_delta_fair(sched_slice(cfs_rq, se), se);
 }
 
+static void update_cfs_load(struct cfs_rq *cfs_rq);
+static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta);
+
 /*
  * Update the current task's runtime statistics. Skip current tasks that
  * are not in our scheduling class.
@@ -558,6 +561,14 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
 
         curr->vruntime += delta_exec_weighted;
         update_min_vruntime(cfs_rq);
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+        cfs_rq->load_unacc_exec_time += delta_exec;
+        if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
+                update_cfs_load(cfs_rq);
+                update_cfs_shares(cfs_rq, 0);
+        }
+#endif
 }
 
 static void update_curr(struct cfs_rq *cfs_rq)
@@ -713,6 +724,7 @@ static void update_cfs_load(struct cfs_rq *cfs_rq)
         }
 
         cfs_rq->load_stamp = now;
+        cfs_rq->load_unacc_exec_time = 0;
         cfs_rq->load_period += delta;
         if (load) {
                 cfs_rq->load_last = now;